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# Board Paper of Class 12-Science 2021 Chemistry Term-I Delhi(Set 4) (Series : SSK/3) - Solutions

General Instructions :
1. This question paper contains 55 questions out of which 45 questions are to be attempted.
2. All questions carry equal marks.
3. This question paper consists of three Sections - Section A, B and C.
4. Section A contains 25 questions. Attempt any 20 questions from Q. No. 01 to 25.
5. Section B contains 24 questions. Attempt any 20 questions from Q. No. 26 to 49.
6. Section C contains 6 questions. Attempt any 5 questions from Q. No. 50 to 55.
7. The first 20 questions attempted in Section A and Section B and first 5 questions attempted in Section C by a candidate will be evaluated.
8. There is only one correct option for every multiple choice question (MCQ). Marks will not be awarded for answering more than one option.
9. There is no negative marking.

• Question 1
Which one of the following pairs will form an ideal solution?
(A) Chloroform and acetone
(B) Ethanol and acetone
(C) n-hexane and n-heptane
(D) Phenol and aniline VIEW SOLUTION

• Question 2
Which of the following is known as amorphous solid?
(A)​ Glass
(B) Plastic
(C) Rubber
​(D) All of the above VIEW SOLUTION

• Question 3
The structure of pyrosulphuric acid is
(A)

(B)

(C)

(D)
VIEW SOLUTION

• Question 4
The C–O–H bond angle in alcohol is
(A) slightly greater than 109°28'.
(B) slightly less than 109° 28'.
(C) slightly greater than 120°.
(D) slightly less than 120°. VIEW SOLUTION

• Question 5
Consider the following reaction:

The major end product is
(A)

(B)

(C)

(D)

VIEW SOLUTION

• Question 6
Nucleosides are composed of
(A) a pentose sugar and phosphoric acid
(B) a nitrogenous base and phosphoric acid
(C) a nitrogenous base and a pentose sugar
(D) a nitrogenous base, a pentose sugar and phosphoric acid VIEW SOLUTION

• Question 7
The oxidation state of –2 is most stable in:
(A) O
(B) S
(C) Se
(D) Te VIEW SOLUTION

• Question 8
Which of the following is not a characteristic of a crystalline solid?
(A) A true solid
(B) A regular arrangement of constituent particles
(C) Sharp melting point
(D) Isotropic in nature VIEW SOLUTION

• Question 9
Which of the following formula represents Raoult's law for a solution containing non-volatile solute?
(A) Psolute = Posolute · Xsolute
(B) P = KH.X
(C) PTotal = Psolvent
(D) Psolute = Posolvent · Xsolvent VIEW SOLUTION

• Question 10
An azeotropic solution of two liquids has a boiling point lower than either of the two when it
(A) shows a positive deviation from Raoult's law
(B) shows a negative deviation from Raoult's law.
(C) shows no deviation from Raoult's law.
(D) is saturated. VIEW SOLUTION

• Question 11
Which of the following crystal will show metal excess defect due to extra cation?
(A) AgCl
(B) NaCl
(C) FeO
(D) ZnO VIEW SOLUTION

• Question 12
Which of the following acids reacts with acetic anhydride to form a compound Aspirin?
(A) Benzoic acid
(B) Salicylic acid
(C) Phthalic acid
(D) Acetic acid VIEW SOLUTION

• Question 13
Which of the following statements is wrong?
(A) Oxygen shows pπ-pπ bonding.
(B) Sulphur shows little tendency of catenation.
(C) Oxygen is diatomic whereas sulphur is polyatomic.
(D) O–O bond is strong than S-S bond. VIEW SOLUTION

• Question 14
Amino acids which cannot be synthesized in the body and must be obtained through diet are known as
(A) Acidic amino acids
(B) Essential amino acids
(C) Basic amino acids
(D) Non-essential amino acids VIEW SOLUTION

• Question 15
Which one of the following halides contains Csp2–X bond?
(A) Allyl halide
(B) Alkyl halide
(C) Benzyl halide
(D) Vinyl halide VIEW SOLUTION

• Question 16
On mixing 20 mL of acetone with 30 mL of chloroform, the total volume of the solution is
(A) < 50 mL
(B) = 50 mL
(C) > 50 mL
(D) = 10 mL VIEW SOLUTION

• Question 17
Consider the following compounds :

the correct order of reactivity towards ${\mathrm{S}}_{\mathrm{N}}2$ reaction
(A) I > III > II
(B) II > III > I
(C) II > I > III
(D) III > I > II VIEW SOLUTION

• Question 18
Which of the following forms strong $\mathrm{p\pi }‐\mathrm{p\pi }$ bonding?
(A) ${\mathrm{S}}_{8}$
(B) ${\mathrm{Se}}_{8}$
(C) ${\mathrm{Te}}_{8}$
(D) ${\mathrm{O}}_{2}$ VIEW SOLUTION

• Question 19
${\mathrm{F}}_{2}$ acts as a strong oxidising agent due to
(A) low  and low
(B) low  and high
(C) high  and high
(D) low  and low  VIEW SOLUTION

• Question 20
Which of the following sugar is known as dextrose?
(A) Glucose
(B) Fructose
(C) Ribose
(D) Sucrose VIEW SOLUTION

• Question 21
Cu reacts with dilute HNO3 to evolve which gas?
(A) N2O
(B) NO2
(C) NO
(D) N2 VIEW SOLUTION

• Question 22
Which of the following is a network solid?
(A) SO2
(B) SiO2
(C) CO2
(D) H2O VIEW SOLUTION

• Question 23
Major product formed in the following reaction

(A)

(B)

(C)

(D)
VIEW SOLUTION

• Question 24
Chlorine reacts with cold and dilute NaOH to give
(A) NaCl and NaClO3
(B) NaCl and NaClO
(C) NaCl and NaClO4
(D) NaClO and NaClO3 VIEW SOLUTION

• Question 25
Elevation of boiling point is inversely proportional to
(A) molal elevation constant (Kb)
(B) molality (m)
(C) molar mass of solute (M)
(D) weight of solute (W) VIEW SOLUTION

• Question 26
An unknown gas 'X' is dissolved in water at 2.5 bar pressure and has mole fraction 0.04 in solution. The mole fraction of 'X' gas when the pressure of gas is doubled at the same temperature is
(A) 0.08
(B) 0.04
(C) 0.02
(D) 0.92  VIEW SOLUTION

• Question 27
The base which is present in DNA but not in RNA, is
(A) Cytosine
(B) Guanine
(D) Thymine  VIEW SOLUTION

• Question 28
In the following reaction

the product formed is
(A)

(B)

(C)

(D)
VIEW SOLUTION

• Question 29
Enantiomers differ only in
(A) boiling point
(B) rotation of polarised light
(C) melting point
(D) solubility VIEW SOLUTION

• Question 30
The number of lone pairs of electrons in XeF4 is
(A) zero
(B) one
(C) two
(D) three VIEW SOLUTION

• Question 31
Sulphuric acid is used to prepare more volatile acids from their corresponding salts due to its
(A) strong acidic nature
(B) low volatility
(C) strong affinity for water
(D) ability to act as a dehydrating agent VIEW SOLUTION

• Question 32
An element with density 6 g cm–3 forms a fcc lattice with edge length of 4 × 10–8 cm. The molar mass of the element is
(NA = 6 × 1023 mol–1)
(A) 57.6 g mol–1
(B) 28.8 g mol–1
(C) 82.6 g mol–1
(D) 62 g mol–1 VIEW SOLUTION

• Question 33
In the reaction compound 'Y' is

(A)

(B)

(C)

(D)
VIEW SOLUTION

• Question 34
Which of the following is the weakest reducing agent in group 15?
(A) NH3
(B) PH3
(C) AsH3
(D) BiH3 VIEW SOLUTION

• Question 35
The boiling point of a 0.2 m solution of a non-electrolyte in water is (Kb for water = 0.52 K kg mol–1)
(A) 100 °C
(B) 100.52 °C
(C) 100.104 °C
(D) 100.26 °C VIEW SOLUTION

• Question 36
Nucleic acids are polymer of
(A) amino acids
(B) nucleosides
(C) nucleotides
(D) glucose VIEW SOLUTION

• Question 37
Which of the following gas dimerises to become stable?
(A) CO2 (g)
(B) NO2 (g)
(C) SO2 (g)
(D) N2O (g) VIEW SOLUTION

• Question 38
In the following diagram point, 'X' represents

(A) Boiling point of solution
(B) Freezing point of solvent
(C) Boiling point of solvent
(D) Freezing point of solution VIEW SOLUTION

• Question 39
XeF6 on reaction with NaF gives
(A) Na+ [XeF7]
(B) [NaF2] [XeF5]+
(C) Na+ [XeF6]
(D) [NaF2]+ [XeF5] VIEW SOLUTION

• Question 40
Glucose on reaction with Br2 water gives:
(A) Saccharic acid
(B) Hexanoic acid
(C) Gluconic acid
(D) Salicylic acid VIEW SOLUTION

• Question 41
Which of the following is optically inactive?
(A) (+) – Butan–2-ol
(B) (–) – Butan–2–ol
(C) (±) – Butan–2–ol
(D) (+) –2 – Bromobutane VIEW SOLUTION

• Question 42
Which of the following is not a correct statement?
(A) Halogens are strong oxidising agents.
(B) Halogens are more reactive than interhalogens.
(C) All halogens are coloured.
(D) Halogens have maximum negative electron gain enthalpy. VIEW SOLUTION

• Question 43
Which of the following has highest boiling point?
(A) C2H5–F
(B) C2H5–Cl
(C) C2H5–Br
(D) C2H5–I VIEW SOLUTION

• Question 44
Which of the following isomer of pentane (C5H12) will give three isomeric monochlorides on photochemical chlorination?

(A)

(B) CH3 CH2 CH2 CH2 CH3

(C)

(D) All of the above VIEW SOLUTION

• Question 45
The question consists of two statements – Assertion (A) and Reason (R).
Assertion (A): A raw mango placed in a saline solution loses water and shrivel into pickle.
Reason (R): Through the process of reverse osmosis, raw mango shrivel into pickle.
Select the most appropriate answer from the options given below:
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is not the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true. VIEW SOLUTION

• Question 46
The question consists of two statements – Assertion (A) and Reason (R).
Assertion (A) : H2S is less acidic than H2Te.
Reason (R) : H–S bond has more ${∆}_{\mathrm{bond}}$ H° than H–Te bond
Select the most appropriate answer from the options given below:
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is not the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true. VIEW SOLUTION

• Question 47
The question consists of two statements – Assertion (A) and Reason (R).
Assertion (A) : Chlorobenzene is less reactive towards nucleophilic substitution reaction.
Reason (R) : Nitro group in chlorobenzene increases its reactivity towards nucleophilic substitution reaction.
Select the appropriate option given below
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is not the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true. VIEW SOLUTION

• Question 48
The question consists of two statements – Assertion (A) and Reason (R).
Assertion (A) : Due to Schottky defect, there is no effect on the density of a solid.
Reason (R) : Equal number of cations and anions are missing from their normal sites in Schottky defect.
Select the appropriate option given below
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is not the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true. VIEW SOLUTION

• Question 49
The question consists of two statements – Assertion (A) and Reason (R).
Assertion (A) : Fluorine forms only one oxoacid HOF.
Reason (R) : Fluorine atom is highly electronegative.
Select the appropriate option given below
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is not the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true.  VIEW SOLUTION

• Question 50
Match the following:  I II (i) Stoichiometric Defects (a) Crystalline solids (ii) Long range order (b) F-centres (iii) .....ABC ABC ABC..... (c) Schottky and Frenkel defects (iv) Number of atoms per unit cell = 2 (d) fcc structure (v) Metal excess defect due to anionic vacancies

Which of the following is the best matched options?
(A) (i) - (d), (ii) - (a), (iii) - (b), (iv) - (c)
(B) (i) - (c), (ii) - (a), (iii) - (d), (v) - (b)
(C) (i) - (c), (ii) - (a), (iii) - (d), (iv) - (b)
(D) (i) - (a), (ii) - (b), (v) - (c), (iv) - (d) VIEW SOLUTION

• Question 51
Which of the following analogies is correct?
(A) XeF2 : linear :: XeF6 : square planar
(B) moist SO2 : Reducing agent :: Cl2 : bleaching agent
(C) N2 : Highly reactive gas :: F2 : inert at room temperature
(D) NH3 : strong base :: HI : weak acid VIEW SOLUTION

• Question 52
Complete the following analogy :
Curdling of milk : A :: $\alpha$-helix : B  (A) A : Primary structure B : Secondary structure (B) A : Denatured protein B : Primary structure (C) A : Secondary structure B : Denatured protein (D) A : Denatured protein B : Secondary structure
VIEW SOLUTION

• Question 53

Case : Read the passage given below and answer the following questions (53-55).

Alcohols and Phenols are acidic in nature. Electron withdrawing groups in phenol increase its acidic strength and electron donating groups decrease it. Alcohols undergo nucleophilic substitution with hydrogen halides to give alkyl halides. On oxidation primary alcohols yield aldehydes with mild oxidising agents and carboxylic acids with strong oxidising agents while secondary alcohols yield ketones. The presence of-OH groups in phenols activates the ring towards electrophilic substitution. Various important products are obtained from phenol like salicylaldehyde, salicylic acid, picric acid etc.

53. Which of the following alcohols is resistant to oxidation?
(A)

(B)

(C)

(D)

VIEW SOLUTION

• Question 54
Case : Read the passage given below and answer the following questions (53-55).

Alcohols and Phenols are acidic in nature. Electron withdrawing groups in phenol increase its acidic strength and electron donating groups decrease it. Alcohols undergo nucleophilic substitution with hydrogen halides to give alkyl halides. On oxidation primary alcohols yield aldehydes with mild oxidising agents and carboxylic acids with strong oxidising agents while secondary alcohols yield ketones. The presence of-OH groups in phenols activates the ring towards electrophilic substitution. Various important products are obtained from phenol like salicylaldehyde, salicylic acid, picric acid etc.

Which of the following group increases the acidic character of phenol?
(A) CH3O–
(B) CH3
(C) NO2
(D) All of these VIEW SOLUTION

• Question 55
Case : Read the passage given below and answer the following questions (53-55).

Alcohols and Phenols are acidic in nature. Electron withdrawing groups in phenol increase its acidic strength and electron donating groups decrease it. Alcohols undergo nucleophilic substitution with hydrogen halides to give alkyl halides. On oxidation primary alcohols yield aldehydes with mild oxidising agents and carboxylic acids with strong oxidising agents while secondary alcohols yield ketones. The presence of-OH groups in phenols activates the ring towards electrophilic substitution. Various important products are obtained from phenol like salicylaldehyde, salicylic acid, picric acid etc.

Consider the following reaction :

the products X and Y are
(A)

(B)

(C)

(D)

VIEW SOLUTION
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